Amplifying system



Aug. 2, 1932. w, CARLSQN 1,870,038

AMPLIFYING SYSTEM Filed May 13, 1925 2 Sheets-Sheet l I lum- Inventor: Wendell L.Cav-ison;

His Attorhea.

2, 1932- w. L. cARLsoN 1,870,038

AMPLIFYING SYS TEM Filed May 13, 1925 2 Sheets-Sheet 2 HT\' I v u l l I I H is Attorney sired to operate Patented Aug. 2, 1932 WENDELL L. CARLSON, OF SCHENECTAIDY,

1,87ac3s PATENT NEW YORK, ASSIGN OR TO GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK AMPLIFYING SYSTEM Application filed May 13,

' My present invention relates to electrical communication, and more particularly to amplifying systems employed in the reception of electrical signals.

This application is a continuation in part of my prior application, Serial No. 589,7 26, filed September 21, 1922, Patent 1,649,098.

An object of my invention is to provide a compact arrangement of the apparatus required in an amplifying system involving the use of a plurality of amplifying valves.

Another object of my invention is to provide a construction for amplifying systems whereby the manufacture may be simplified and the cost reduced.

My invention is especially adapted to a radio frequency amplifying system, and will be described herein in connection withsuch a system, but it is to be understood that it is 329 also applicable to a system for amplifying audio frequency currents.

Heretofore it has been customary to construct individual transformers for each stage of a thermionic cascade amplifier and mount ,35 them so that they will be separated by sub- I have found, however, that it is possible to assemble the various transformer windings of a cascade amplifier all on a single iron core shell'in such a way stantial distances.

that part of the iron magnetic path will be common to adjacent sets of windings without introducing operating difiiculties due to feedback of energy from one circuit to a preceding circuit. In cases where the amplifier is deover an extremely wide range of frequencies, the individual. windings o the transformer units may be designed differently though assembled onone shell, and the leads connected toa suitable switch so as to connect alternately the proper transformer with the amplifier circuit to operate on the particular frequency range for which it is designed.

The novel features which I believe to be g, characteristic of my invention are set forth with particularity in the appended claims. My invention itself however both as to its organization and method of operation will best be understood by reference to the followas ing description taken in connection with the f lead of amplifier 3 is connected to simultaneously with arm 11 to 1925. Serial N0. 30,036.

accompanying drawings in which Fig. 1

shows diagrammatically a radio receiving circuit employing three radio frequency stages-of amplification and a detector. Fig. 2 shows diagrammatically a radio receiving circuit employing one radio frequency stage of amplification and a detector tube, and three radio frequency transformers, each designed to operate over a different frequency range. Fig. 3 is aplan view of three radio frequency transformers mounted on a single iron core which are adapted to be employed in the circuits shown in Figs. 1 and 2; and Fig. 4 is a diagrammatic representation of a superheterodyne radio receiving system showing one high frequency transformer and three intermediate frequency transformers mounted on a single iron core.

In the arrangement shown in Fig. 1 the tuned antenna circuit 1 is coupled to a secondary tuned circuit 2, which in turn is connected to the input of an electron discharge amplifier 3. The output of amplifier 3 is coupled by theradio frequency transformer 4 to the input of amplifier 5. The output'of amplifier 5 is in like manner coupled to the output of the third amplifier 7 by a coupling transformer 6. Transformer 8 couples the output of amplifier 6 to the input of a detector 9 which has a telephone receiver 10 connected in its output circuit.

In the arrangement of Fig. 2 the antenna 1 is coupled to the secondary tuned circuit 2 which is connected tothe input of the electron discharge amplifier 3. The plate I the switch arm 11 which is adapted to make contact with points 12, 13 and 1 1 as the arm is rotated at the will of the operator. In like manner, the switch arm 15 may be rotated make contact with points 16, 17 and 18. The primary windings of transformers 19, 20 and 21 are connected at one end to contact points 12, 13 and 14, and the other ends, known as the low potential terminals, are connected'to a common terminal andjto the plate battery 22. Thesecondary windings of transformers 19, 20 and 21 are connected at their high potential ends to points 16, 17 and 18 and their low potential ends are commonly connected to the cathode of detector 9.

In the transformer arrangement shown in Fig. 3 the radio frequency transformers 4, 6 and 8 of Fig. l, or 19, and 21 of Fig. 2, are indicated in the manner in which they may be mounted in the transformer unit. Each individual transformer has its own primary and secondary winding wound on a small laminated iron core plug 23. The laminated iron shell 24 having legs 25 completes the magnetic path around the coils, forming what are generally known as shell type transformers. Air gaps 26 are preferably provided between the core plugs 23 and the shell 24 in order to reduce the iron losses and regulate the permeability of the magnetic path.

The operation of the system shown in Fig. 1 is so well known in the art that it is not necessary to dwell on it extensively here, it being sufficient to say that the radio carrier wave of the incoming signal is amplified by means of the three amplifiers 3, 5 and 7, and that the modulating component of the carrier frequency actuates the tele phone receiver 10 due to the rectifying action of detector 9. It has hereto-fore been believed that the magnetic coupling between adjacent individual transformers in such a construction as that herein disclosed, would create local oscillations in the accompanying amplifier circuits. I have found, however, that the stray magnetic coupling existing with such a transformer construction on short wave lengths is practically negligible so far as the creation of local oscillations is concerned. .If on low radio frequencies or audio frequencies it is found that due to the greater penetration of the field in the iron the coupling between the adjacent individual transformers creates troublesome effects, then by properly connecting the adjacent windings of the transformers, i. e. all windings in the same directions, the 0s cillating tendency of the system will be eliminated. Y

The operation of the system shown in Fig. 2 is identical to the operation of the circuit shown in Fig. 1 except that-only one amplifier 3 is employed in conjunction with the individual transformers 19, 20 and 21,-and detector 9. The individual transformers 19, 20 and 21 are designed to cover different wave length ranges, i. e., they differ in construction and number of turns, and air gaps'26 between the shell 24 and plugs 23, by switching to the proper transformer good amplification can be obtained over therange which 5 the transformer is designed to cover. While only one radio stage is shown in this case, it is obvious thatany practical number of stages and a corresponding number of transformer units may be employed.

In the super-heterodyne system shown in Fig. 4 I have indicated a radio amplifying tube 27 to the input circuit of which received signals are supplied from a tuned loop 28. The output of tube 27 includes a primary 29 of a radio frequency transformer, which is mounted on a plug 30' and coupled to a secondary winding 31, which is included in the input circuit of detector tube 32. Local oscillations from an oscillator tube 33 are also supplied to this input circuit of detector tube 32 through the coupling transformer 34.

By the means thus far described, currents of a frequency lower than that of the received currents are supplied to the primary Windin 35 of an intermediate frequency transformer 36. The secondary 37 of this transformer is connected to the input of an amplifier 38 and the output circuit of 38 in turn includes the primary winding 39 of a second intermediate frequency transformer 40. The secondarv 41 of transformer is connected to the input of a second intermediate amplifier 42, the output Of which in turn includes the primary 43 of the third intermediate frequency transformer 44. The secondar 45 of intermediate transformer 44 is connected to the input of detector 46.

Ihave found it desirable in the arrangement described to employ magnetic shunts 47 for the first two intermediate frequency transformers to reduce the coupling between primary and secondary windings. Air gaps of suitable dimensions may be provided between the plugs 30 and 48 upon which the transformers are wound and the shell 49.

In order to prevent the tendency for production of oscillations in the intermediate frequency amplifying tubes by reason of capacity feed-back, the windings of the successive intermediate frequency transformer may be so located as to provide a magnetic feed-back from the output circuit of tube 42, for example, to the input circuit, to counteract the capacity feed-back through the tube. Since the intermediate frequency transformers are intended to be operated at .a single frequency a neutralization of the oscillation tendency produced in this way can be affected which is correct for any signaling frequency which may be received.

It will of course be understood that the circuit arrangement shown in Fig. 4 is purely diagrammatic and includes only the es sential parts of the circuit in order to simplify the drawings. Yet in practice many modifications may be made in the circuit, such for example, as the provision of common A and B batteries for all of the tubes, and in some cases, condensers for tuning the various windings if desired. Such modifications, however, do not affect the fundamental structure of the common transformer unit.

l/Vhat I claim as new and desire to secure by Letters Patent of the United States, is:

1. The combination in an amplifying system of a plurality of electron discharge amplifiers connected in cascade and an iron core having mounted thereon a plurality of sets of transformer windings, said transformer windings serving to connect the output circuits of a plurality of amplifiers to the input circuits of a plurality of amplifiers, at least one of said amplifiers being connected to amplify radio frequency currents of a received signaling frequency and another of said amplifiers being connected to amplify currents of a different frequency.

2. The combination in an amplifying system of a plurality of electron discharge amplifiers connected in cascade and an iron core having mounted thereon a plurality of sets of transformer windings, said transformer windings serving to connect the output circuits of a plurality of amplifiers to the input circuits of a plurality of amplifiers, at least one of said amplifiers being connected to amplify radio frequency currents of a received signaling frequency and another of said amplifiers being connected to amplify currents of a different radio frequency which is lower than that of the received signaling currents.

3. The combination in an amplifying system of a plurality of electron discharge amplifiers connected in cascade and an iron core having mounted thereon a plurality of sets of transformer windings, said transformer vinciings serving to connect the output cir cuits of a plurality of amplifiers which are connected to amplify radio frequency cur rents of a lower frequency from that to be received, to the input circuits of a plurality of amplifiers.

4. lhe combination in an amplifying system of a plurality of electron discharge amplifiers connected in cascade and an iron core having mounted thereon a plurality of sets of transformer windings, said transformer windings serving to connect the output circuits of a plurality of amplifiers to the input circuits of a plurality of amplifiers certain of said transformer windings being so related to other of said transformer windings as to provide a magnetic coupling from one output circiut to a preceding input circuit which opposes the effect of other couplings between said circuits.

5. The combination in an amplifying system of a plurality of electron discharge devices connected in cascade and an iron core having mounted thereon a plurality of sets of transformer windings, one set of said windings serving to connect the output circuit of an amplifier which is adapted to amplify received signaling currents of radio frequency to the input circuit of a detector and a plurality of other sets of windings serving to connect the output circuits of a plurality of amplifiers which are connected to amplify radio frequency currents of a lower frequency than that received, to the input circuits of a plurality of amplifiers.

6. The combination in an amplifying system of a plurality of electron discharge amplifiers connected in cascade, and transformer means for connecting the output circuits of a plurality of said amplifiers to the input circuits of a plurality of said amplifiers comprising a shell of magnetic material having a plurality of parallel legs, a plurality of sets of transformer windings mounted on cores which are inserted between adjacent parallel legs, and a magnetic shunt interposed between the primary and secondary winding of at least one set of said windings.

7. The combination in an amplifying system of a plurality of electron discharge amplifiers connected in cascade, and transformer means for connecting the output circuits of a plurality of said amplifiers to the input circuits of a plurality of said amplifiers comprising a shell of magnetic material having a plurality of parallel legs, a plurality of sets of transformer windings mounted on cores which are inserted between adjacent parallel legs, adjacent sets of said windings being arranged to provide a magnetic coupling from the output circuit of one amplifier to a preceding input circuit which opposes the eifect of other couplings between the circuits. 1

8. In combination, a plurality of electric discharge devices adapted to be connected in tandem, an inter-stage transformer having a primary winding connected to the output electrodes of one of said devices and a secondary winding connected to the input electrodes of another of said devices, a core struc- 'ture for said inter-stage transformer, an inut transformer for saidfirst device, a core structure for said inputtransformer having a leg in common with the core for said interstage transformer, an output transformer for said second device and a core structure for said output transformer having a leg in common with the core for said inter-stage transformer.

9. In combination, a vacuum tube having input and output terminals, an inductive winding connected to said input terminals, a second inductive winding connected to said output terminals, a core and magnetic circuit for one of said windings, a different core and different magnetic circuit for the other said winding, and means for passing aportion only of the flux in the second inductive winding through the first inductive windin 10. In combination, a vacuum tube having input and output terminals, an inductive winding connected to said input terminals, a second inductive winding connected to said output terminals, a core and magnetic circuit for one of said windings, a different core and different magnetic circuit for the other said winding, and means comprising a portion common to the two core structures to provide coupling between said windings.

11. In combination, a vacuum tube having input and output terminals, an input transformer whose secondary is connected to said input terminals, an output transformer whose primary is connected to said output terminals, means for causing a portion only of the flux in the primary of the output transformer to pass through the secondary of the input transformer.

12. A combination according to the preceding claim in which said transformers are of the shell type and in which the means for causing a portion only of the flux in the primary of the output transformer to pass through the secondary of the input trans former comprises an intermediate flux carrying member which is common to the magnetic circuits of both transformers.

13. In combination, a transformer comprising a primary coil and a secondary coil and a core member extending therethrough, a second transformer comprising a primary coil and a secondary coil and a second core member extending therethrough, a first member of magnetic material extending around said transformers and cooperating with one end of each of said cores for the passage of flux, a second member of magnetic mate rial cooperating with the other end of each of said cores and with said first member of magnetic material for the passage of flux whereby there is a different magnetic circuit for each transformer, with the second magnetic member common to both of said circuits, and a portion only of the flux in one of the cores passes through the other core.

In witness whereof, I have hereunto set my hand this 11th day of May, 1925.

WENDELL L. CARLSON. 

